This invention relates generally to a strain relief assembly for reducing bending of a welding cable, and more particularly, to a strain relief assembly having at least two strain relief elements for supporting the welding cable.
Gas metal arc welding ("GMAW", also known as "metal, inert-gas" welding or "MIG" welding) is used to join pieces of metal. GMAW is performed using a welding system comprising a welding machine and a welding gun joined by a welding cable. The welding machine feeds welding wire through the welding cable to the welding gun which is held adjacent a workpiece. The machine also delivers electricity to the welding gun for producing an arc between the wire and the workpiece to melt the wire into a molten pool of metal for joining the pieces of metal. In addition, the machine supplies inert welding gas to the welding gun to shield the molten pool of metal from the atmosphere. The welding cable includes electrically conductive wires for delivering electricity to the welding gun, a hose for delivering inert welding gas to the welding gun, and a conduit for delivering welding wire to the welding gun.
As the welding operator manipulates the welding gun over the workpiece, the welding cable connecting the welding gun to the welding machine bends. The cable also bends under its own weight. Because the welding machine is a stationary unit, the cable tends to bend most sharply at the end where it enters the machine. The cable also tends to bend sharply at the end adjacent the welding gun due to the movements of the operator.
When the welding cable bends, the drag between the welding wire and the inside surface of the conduit increases. If the cable is bent too sharply, the drag force on the wire will intermittently slow the wire feed rate, producing chatter, preventing smooth delivery of the welding wire to the workpiece and degrading the quality of the weld produced. If the cable is bent still more sharply, the welding wire can seize in the conduit. If the machine continues to feed wire when the wire seizes, the wire can break and cause the system to malfunction. In addition, as the cable bends, the hose delivering welding gas to the workpiece may become pinched, thereby reducing welding gas flow to the workpiece. If the gas flow rate is reduced too much, the molten metal may become exposed to the atmosphere resulting in an inferior weld. Moreover, excessive repeated bending can cause the electrical wires inside the cable to fatigue and break, causing increased electrical resistance and heat generation in the cable. If the heat generated becomes too great, the performance of the welding gun is decreased and the gun may malfunction.
In the past, strain relief assemblies have been attached to the cable where it enters the welding gun and welding machine to support the cable and reduce bending. One such strain relief comprises an elastomeric sleeve which surrounds the cable. These sleeves are generally stiff when new causing the cable to bend more sharply where it enters the sleeve, thereby defeating, at least to some extent, the purpose of the sleeves. Further, these sleeves lose their resilience over time, due to heat and fatigue, and eventually take on a permanent set which induces bending in the welding cable. Still further, these sleeves are susceptible to tearing which allows the cable to bend. Another type of previously-used strain relief assembly comprises a resilient coil spring which surrounds the cable. These springs are generally not as stiff as the elastomeric sleeves so they do not support the cable as well. Further, the springs tend to catch on surrounding objects making the cables difficult to use. Still further, the springs have a relatively large pitch (e.g., 0.250 inch) which increases their tendency to catch on surrounding objects.